Hi, everyone.
We have a R50-15 Still forklift which has some problems with its electric power steering system.
We recently sent it to a repair workshop where they assessed that it was a problem with both the steering motor and its control board and so they said they would need to repair the motor and change the entire electric system.
To change the electric system they asked about 4000€ so we decided to first try to fix the control board ourselves.

I couldn't find the electrical schematic of the board, as Still doesn't provide it, so I tried to just change the old electrolytic capacitors on the board.
This at first seemed to apparently fix the problem so gave the ok to the repair workshop to proceed with overhauling the motor.

With the motor overhauled they tested again the entire system but a new problem arise.

When the forklift is turned on the power steering initially works but the coupling between the magnet on the steering wheel and the magnetic sensor on the motor's shaft seems to be unstable.
If the the wheel is stirred to fast or the torque is increased after a certain threshold (we measured about 6V output from the board) the sensor slips and gets decoupled from the magnet.

In the workshop manual I found a calibration procedure for this sensor, I will try it as soon as I can but I doubt that this will solve the problem.

Has anyone encountered a similar problem or does anyone know where I can find the electrical schematic for the electric power steering control board for this model of forklift?

Thank you everyone in advance.

PS I'll attach a link to the R50-15 workshop manual that I managed to find online for anyone that could need it.
https://drive.google.com/file/d/1US00i34TJ0insgWHBbJB_zwG-I2vwujZ/view?usp=drive_link